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[PATCH v4 08/25] block: introduce assert_bdrv_graph_writable
From: |
Emanuele Giuseppe Esposito |
Subject: |
[PATCH v4 08/25] block: introduce assert_bdrv_graph_writable |
Date: |
Mon, 25 Oct 2021 06:17:18 -0400 |
We want to be sure that the functions that write the child and
parent list of a bs are under BQL and drain.
BQL prevents from concurrent writings from the GS API, while
drains protect from I/O.
TODO: drains are missing in some functions using this assert.
Therefore a proper assertion will fail. Because adding drains
requires additional discussions, they will be added in future
series.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block.c | 5 +++++
block/io.c | 11 +++++++++++
include/block/block_int-global-state.h | 10 +++++++++-
3 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index 41c5883c5c..94bff5c757 100644
--- a/block.c
+++ b/block.c
@@ -2734,12 +2734,14 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
if (child->klass->detach) {
child->klass->detach(child);
}
+ assert_bdrv_graph_writable(old_bs);
QLIST_REMOVE(child, next_parent);
}
child->bs = new_bs;
if (new_bs) {
+ assert_bdrv_graph_writable(new_bs);
QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent);
/*
@@ -2940,6 +2942,7 @@ static int bdrv_attach_child_noperm(BlockDriverState
*parent_bs,
return ret;
}
+ assert_bdrv_graph_writable(parent_bs);
QLIST_INSERT_HEAD(&parent_bs->children, *child, next);
/*
* child is removed in bdrv_attach_child_common_abort(), so don't care to
@@ -3140,6 +3143,7 @@ static void bdrv_unset_inherits_from(BlockDriverState
*root, BdrvChild *child,
void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child)
{
assert(qemu_in_main_thread());
+ assert_bdrv_graph_writable(parent);
if (child == NULL) {
return;
}
@@ -4903,6 +4907,7 @@ static void bdrv_remove_filter_or_cow_child_abort(void
*opaque)
BdrvRemoveFilterOrCowChild *s = opaque;
BlockDriverState *parent_bs = s->child->opaque;
+ assert_bdrv_graph_writable(parent_bs);
QLIST_INSERT_HEAD(&parent_bs->children, s->child, next);
if (s->is_backing) {
parent_bs->backing = s->child;
diff --git a/block/io.c b/block/io.c
index f271ab3684..1c71e354d6 100644
--- a/block/io.c
+++ b/block/io.c
@@ -740,6 +740,17 @@ void bdrv_drain_all(void)
bdrv_drain_all_end();
}
+void assert_bdrv_graph_writable(BlockDriverState *bs)
+{
+ /*
+ * TODO: this function is incomplete. Because the users of this
+ * assert lack the necessary drains, check only for BQL.
+ * Once the necessary drains are added,
+ * assert also for qatomic_read(&bs->quiesce_counter) > 0
+ */
+ assert(qemu_in_main_thread());
+}
+
/**
* Remove an active request from the tracked requests list
*
diff --git a/include/block/block_int-global-state.h
b/include/block/block_int-global-state.h
index d08e80222c..6bd7746409 100644
--- a/include/block/block_int-global-state.h
+++ b/include/block/block_int-global-state.h
@@ -316,4 +316,12 @@ void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
*/
void bdrv_drain_all_end_quiesce(BlockDriverState *bs);
-#endif /* BLOCK_INT_GLOBAL_STATE*/
+/**
+ * Make sure that the function is either running under
+ * drain and BQL. The latter protects from concurrent writings
+ * from the GS API, while the former prevents concurrent reads
+ * from I/O.
+ */
+void assert_bdrv_graph_writable(BlockDriverState *bs);
+
+#endif /* BLOCK_INT_GLOBAL_STATE */
--
2.27.0
- [PATCH v4 00/25] block layer: split block APIs in global state and I/O, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 03/25] assertions for block global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 01/25] main-loop.h: introduce qemu_in_main_thread(), Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 04/25] include/sysemu/block-backend: split header into I/O and global state (GS) API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 02/25] include/block/block: split header into I/O and global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 05/25] block/block-backend.c: assertions for block-backend, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 08/25] block: introduce assert_bdrv_graph_writable,
Emanuele Giuseppe Esposito <=
- [PATCH v4 07/25] assertions for block_int global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 06/25] include/block/block_int: split header into I/O and global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 12/25] assertions for blockob.h global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 11/25] include/block/blockjob.h: global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 10/25] assertions for blockjob_int.h, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 09/25] include/block/blockjob_int.h: split header into I/O and GS API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 14/25] include/systemu/blockdev.h: global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 15/25] assertions for blockdev.h global state API, Emanuele Giuseppe Esposito, 2021/10/25
- [PATCH v4 16/25] include/block/snapshot: global state API + assertions, Emanuele Giuseppe Esposito, 2021/10/25